I was wondering when this point was going to surface. Yes, the fact there is one planet that has defied the odds and supports life makes the statistical case that there are other planets out there that can also support life. No-one can argue against that simple exercise in probability, but it's also just that, a very simplistic way of thinking about this. The good thing is, there is math to try and quantify this. However the problem lies in the variables and their consensus around a definition on how to report them. There is an equation called the drake equation that attempts to put a number on a possibility of life in our own milky way galaxy. I'll save you the time and just tell you it's very very very small. If you want to do the math yourself, look up and enjoy.
The universe is more than 13 billion years old. That means that even if there have been a thousand civilizations in our own galaxy, if they live only as long as we have been around, roughly ten thousand years, then all of them are likely already extinct. Asteroids are bad for civilizations, it turns out. Then others won’t evolve until we are long gone. For us to have much chance of success in finding another "contemporary" active technological civilization, on average they must last much longer than our present lifetime. Given the vast distances between stars and the fixed speed of light we might never really be able to have a conversation with another civilization anyway. If they were 20,000 light years away then every exchange would take 40,000 years to go back and forth. So in reality, by the time we know of life out there...they already may be extinct in real time.
